Volcán Poás Heating Up
This past Friday in the early morning the Poás Volcano made an eruption consisting of agua and sediments. This type of eruption is known by scientists as a “phreatic” (or “steam-blast) eruption. The plume reached a height of 300 meters. Wikipedia describes such eruptions as being driven by explosive expanding steam resulting from cold ground or surface water coming into contact with hot rock or magma. The distinguishing feature of phreatic explosions is that they only blast out fragments of pre-existing solid rock from the volcanic conduit; no new magma is erupted. The eruption threw fragments of sediment onto the mirador where tourists overlook the volcano’s massive crater, one of the largest active craters in the world. Poás is unique in that in the bottom of the crater there is a usually blue, or greenish blue, colored lake of very hot water. Normally the temperature of the water hovers between 100 and 135 degress centigrade. However, lately the temperature has risen to 369 degress centigrade. Raúl Mora, vulcanologist, told La Nación, that the last time a phreatic eruption was recorded at Poás was in July of 1994, when the crater’s highly acidic lake dried up. Another recent phenomenon associated with the rising temperature of the lake is the combustion of sulfur, which only occurs at Poás when the lake’s temperature exceeds 248 degrees centigrade. Scientists inform that since December of 2008 the lake has lost some 400,000 cubic meters of liquid due to the high temperatures of the water and the lack of rain. Mora added that the volcano must continue to be observed with vigilance as the sulphuric gases that are being emitted can be very hazardous to humans, especially the tourists who flock to the volcano’s mirador to snap photos of the awe-inspiring crater.
December 3rd, 2009 at 2:37 am
[...] the volcano. The result is that the lake may completely dry up, or there may be the phenomenon of Phreatic eruptions, as actually occurred at Poás the 18th of September this [...]